(AP) CHICAGO Tim Pierce hopes he never has to depend on a new state anti-discrimination law protecting gays and lesbians. But if he does, he's glad the protection is there.

The 39-year-old university instructor and his partner live in Oswego -- a town about 40 miles west of Chicago and one of several in the state that didn't have laws protecting gays and lesbians. That is, until now.

On Sunday, a state law prohibiting discrimination based on sexual orientation and gender identity will become a reality, nearly a year after Gov. Rod Blagojevich signed it into law and more than three decades since state lawmakers first debated it.

"I'm hoping people won't need to rely on the law," said Pierce, who also is the president of a gay rights organization in Joliet. "But in instances where someone is denied housing or a job, they have an avenue to take that they couldn't before."

Illinois joins 15 other states that have laws banning discrimination based on sexual orientation. Of those 16, Illinois is only one of seven states where the law protects transgender people, according to the Washington-based National Gay and Lesbian Task Force.

"Illinois is not a trendsetter, but it's not a right-winger," said Rick Garcia, political director for the gay rights group Equality Illinois. "We're not Massachusetts or California, but we're certainly not Alabama or Tennessee. ... Illinoisans are reasonable people. We are cautious, but we want to do the right thing."

Some opponents worry the law will put Illinois on the path to legalizing gay marriage, a concern advocates dismiss.

The battle to ban sexual-orientation discrimination in Illinois began in the mid-1970s, when the first bills were introduced into the Legislature.

Though bill after bill went by the wayside, communities across the state began amending their own anti-discrimination laws to include sexual orientation. Champaign was the first in 1977, followed by Urbana, Chicago, eight other cities and Cook County.

Chicago-based Equality Illinois joined the fight in the early 1990s, making the anti-discrimination amendment its top priority. It took more than a dozen more years for the Legislature to make it happen.

In 2005, the state House passed the anti-discrimination bill 65-51 on the last possible day before it would have died. The bill barely slid through the Senate by a 30-27 vote, the minimum number required. Blagojevich signed it into law on Jan. 21.

For Equality Illinois' Garcia, the battle has been a long and frustrating one, but he doesn't want to complain -- too much.

"It took 30 years for it (the Legislature) to pass something as simple as protecting people on the basis of sexual orientation," Garcia said. "On one hand, the Illinois General Assembly should be commended for recognizing all Illinoisans should be treated the same. But on the other hand, what the hell took so long?"

The law allows people to file complaints with the Illinois Department of Human Rights if they believe they were denied a job, housing, public accommodation or credit.

For many in Illinois, the Human Rights amendment won't change their lives. Supporters have said about half of the state's population already lives in areas protected by local ordinances. But in Oswego or Danville or Belleville, the law marks the first time gays, lesbians, bisexuals and transgender people can legally fight back.

"I think it's (the law) not going to have a lot of affect in places like Chicago and Cook County, but if you're in Pekin, Prairie du Rocher, Red Bud or Zion, you'll be protected," Garcia said.

But not everyone believes adding sexual orientation to the Human Rights Act will benefit the state.

State Sen. Peter Roskam, R-Wheaton, said he worries the law is not clear on its definition of sexual orientation and doesn't protect religious institutions from being forced to hire gays and lesbians.

"I think it's going to lead to some unpleasant situations," said Roskam, who voted against the bill.

Roskam, who is running for retiring U.S. Rep. Henry Hyde's seat in Congress, also fears the law is "a building block for gay marriage."

State Senate Minority Leader Frank Watson, R-Greenville, who also voted against the bill, said the law will cause some politicians to push harder for laws prohibiting gay marriage.

"The sexual orientation legislation has promulgated the push to pass the ban on same-sex marriage," he said.

Gay rights advocates say their opponents' fears are unfounded.

Sen. Carol Ronen, D-Chicago, the chief sponsor of the anti-discrimination bill that Blagojevich signed, said she doesn't think the law will lead the state to legalize gay marriage.

"That's a whole other area and another arena of discussion," Ronen said. "I think Illinois is far away from that."

Buff Carmichael, who publishes Prairie Flame, a monthly newspaper geared to the gay community outside of Chicago, said Illinois' law lags behind public opinion.

"The mood of the public has been more accepting in recent years than in times past," said Carmichael, who lives in Springfield. "We don't get kicked out of as many places as years ago."

Still, Carmichael, said it's about time the gay community received equal protection.

"I would've hated to be the only gay person in some town in the Carbondale area and be looking for a job. But to have this law now, if you can prove it, they can't refuse to hire you anymore based on orientation," he said.